JPH0755275A - Apparatus and method for controlling operation of refrigerator - Google Patents

Abstract

PURPOSE:To suppress an internal pressure rise of a refrigerant tank by providing means for so controlling a refrigerant flow rate as to return, after it is switched to a set flow rate less than a normal flow rate, it to the normal flow rate after energization or deenergization is finished. CONSTITUTION:When a superconducting magnet is energized or deenergized, refrigerant flowrate regulating means 19 is controlled by control means 54 which receives an output signal of energizing and deenergizing operation detecting means 53, a refrigerant flow rate to a refrigerant tank Th is switched from a normal flow rate to '0' during executing of energization or deenergization of the magnet. When it is returned to the flow rate after the energization or the deenergization of the magnet is finished, it is returned to the normal flow rate after it is switched to a set flow rate less than the normal flow rate. Thus, a pressure of the refrigerant from compressors 4, 8 to the tank Th is lowered while the flow rate remains the set flow rate to reduce the flow rate, thereby effectively suppressing an internal pressure rise of the tank Th over a peak value during the energization or the deenergization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is attached to a refrigerant tank for storing a liquefied refrigerant for cooling a superconducting magnet of a linear motor car to a cryogenic level, and sucks refrigerant gas evaporated in the refrigerant tank into a refrigerant circuit. The present invention relates to an operation control device and an operation control method for a refrigerator for a linear motor car which is liquefied by compression and expansion and returned to the inside of a tank.

[0002]

2. Description of the Related Art In recent years, a linear motor car equipped with a superconducting magnet has attracted attention. In this superconducting magnet, liquid helium stored in the tank is used to cool and maintain the superconductor used for the coil below the critical temperature, but since this liquid helium evaporates in the tank, this evaporated helium is used. It is necessary to cool and condense the gas to liquefy it, and a cryogenic refrigerator is used for this purpose.

As an example of a refrigerator for cooling the helium gas to a condensing temperature, there is a conventional one, for example, US Pat. No. 4,223.
No. 540, etc., a pre-cooling refrigerator and a J-
There is a refrigerator combined with a T refrigerator. The above pre-cooling refrigerator is a GM cycle (Gifford McMahon cycle)
And a refrigerating machine such as an improved solve cycle. The helium gas (refrigerant gas) compressed by the compressor is adiabatically expanded by the expander, and the temperature drop of the gas causes the cryogenic cold level at the heat station. .

On the other hand, the JT refrigerator has a precooler for precooling by exchanging heat between the helium gas supplied from the compressor and the heat station of the expander in the precooling refrigerator, and the helium gas in a joule. Thomson inflates J-
It is connected with a T valve, and helium gas from the compressor is precooled by a precooler, and the precooled helium gas is expanded by Joule-Thomson with the JT valve to generate 4K level cold. It is like this.

When the evaporated helium gas in the tank is cooled by a refrigerator, two refrigerant pipes are arranged in the tank so that one end of each refrigerant pipe opens into the tank and the other end of both pipes is arranged. Is taken out of the tank and connected in series to the refrigerant circuit of the JT refrigerator, so that the inside of the tank becomes a part of the refrigerant circuit of the refrigerator, and the evaporated helium gas in the tank is JT frozen from one pipe. Sucked into the refrigerant circuit of the machine and compressed by the compressor, the compressed helium gas is expanded by the JT valve to be cooled and liquefied, and this liquid helium is returned to the tank through the other pipe. Has been done.

By the way, the internal pressure of the liquid helium tank for cooling the superconducting magnet of the linear motor car to a critical temperature or lower is within a predetermined range (0.15 to 0.15) during normal operation of the refrigerator.
The balance is about 0.25 kg / cm ² G). However, when degaussing for stopping the generation of the magnetic field by the superconducting magnet or exciting by applying an electric current from the outside for maintenance or inspection of the linear motor car, the heat load increases and the pressure in the tank rises. When the tank internal pressure exceeds the upper limit value (for example, 0.4 kg / cm ² G), the safety valve operates to evaporate the helium gas in the tank to the outside of the tank.

In order to avoid the operation of this safety valve, conventionally,
When performing the demagnetization of the superconducting magnet, the operating frequency of the compressor in the JT refrigerator is increased to increase the suction amount of the helium gas sucked from the liquid helium tank into the compressor, and the refrigerant of the JT refrigerator. Operate the refrigerator in an excitation / demagnetization mode that temporarily reduces the gas flow rate in the circuit to 0 or lowers it from the normal flow rate (gas flow rate during normal operation of the superconducting magnet) to reduce the gas flow rate into the tank. As a result, the tank internal pressure is reduced and the difference from the suction amount into the compressor is stored in the buffer tank.

[0008]

When the excitation / demagnetization of the superconducting magnet is performed in this manner, the rise in the tank internal pressure can be effectively suppressed as the gas flow rate decreases. However, when the gas flow rate is returned to the normal flow rate after the excitation / demagnetization, the helium gas rapidly returns to the inside of the tank, so that the tank internal pressure may rise again to a level exceeding the peak pressure accompanying the excitation / demagnetization.

In order to suppress the re-rise of the tank internal pressure to a low level, it is necessary to continuously operate the refrigerator in the excitation / demagnetization mode after the demagnetization of the superconducting magnet is completed until the tank internal pressure is reduced to some extent. However, in that case, the operating frequency of the compressor is kept high for a long period of time due to long-term excitation / demagnetization mode operation, and its durability decreases, and the flow rate balance between reciprocating gases in the refrigerant circuit is reduced. Collapse and the temperature of the return gas to the compressor decreases, frost is formed on the return side connecting pipe, the performance of the lubricating oil decreases due to the suction of low temperature helium gas of the compressor, and the performance of the liquid helium tank is reduced. This causes problems such as an increase in the amount of gas evaporation and an increase in the amount of helium recovered in the buffer tank.

The present invention has been made in view of the above points, and an object thereof is to effectively increase the internal pressure of the refrigerant tank by changing the operation control mode of the refrigerator after the demagnetization of the superconducting magnet. To try to suppress it.

[0011]

In order to achieve the above object, in the present invention, the refrigerant flow rate in the refrigerator is not returned to the normal flow rate at once after the end of the demagnetization of the superconducting magnet.
The flow was returned via an intermediate flow rate that is lower than the normal flow rate.

Specifically, in the invention of claim 1, as shown in FIG. 1, a refrigerant tank (T for storing a liquid refrigerant for cooling and holding the superconducting magnet of the linear motor car to a critical temperature or below) is stored.
In h), compressors (4), (8) and expansion means (38)
Of the refrigerant tank (T
The gas refrigerant evaporated in h) is sucked into the refrigerant circuit, compressed by the compressors (4) and (8), and then expanded by the expansion means (38), and a liquid refrigerant is generated by the temperature drop due to the expansion, thereby generating the refrigerant. It is premised on a refrigerator for a linear motor car that is returned into the tank (Th).

A refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4), (8) to the refrigerant tank (Th) and an excitation for detecting that the superconducting magnet is demagnetized. Upon receiving the demagnetization operation detection means (53) and the output signal of the detection means (53), the refrigerant flow rate to the refrigerant tank (Th) is switched from the normal flow rate to 0 during the excitation / demagnetization of the superconducting magnet to end the excitation / demagnetization. After that, a control means (54) for controlling the refrigerant flow rate adjusting means (19) is provided so as to return the flow rate to the normal flow rate after switching the flow rate of the refrigerant to a set flow rate lower than the normal flow rate.

According to the second aspect of the present invention, when the superconducting magnet is excited and demagnetized, the refrigerant flow rate is set to a set flow rate other than 0, and after the end of the excitation and demagnetization, the refrigerant is changed from the set flow rate to the normal flow rate through a larger intermediate flow rate. I'm trying to bring it back.

That is, according to the present invention, as in the case of the first aspect of the present invention, the refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), An excitation / demagnetization operation detection means (53) for detecting the excitation / demagnetization of the superconducting magnet is provided.

Further, the refrigerant tank (Th) is received while the superconducting magnet is being demagnetized by receiving the output signal of the detecting means (53).
Is switched from the normal flow rate to the first set flow rate which is smaller than the normal flow rate, and after the completion of the demagnetization, the refrigerant flow rate is set to the second set flow rate which is lower than the normal flow rate and higher than the first set flow rate. Control means (5) for controlling the refrigerant flow rate adjusting means (19) so as to return to the normal flow rate after switching.
4) is provided.

In a third aspect of the invention, a desirable configuration of the refrigerant flow rate adjusting means is embodied. That is, in the present invention, the refrigerant flow rate adjusting means (19) includes the compressor (4),
Refrigerant piping (15) from (8) to the refrigerant tank (Th)
A plurality of branch pipes (15a), (1
5b), ... and the branch pipes (15a), (15b),
... and throttle valves (V
1), (V2), ... And each branch pipe (15a), (15
b), ... Open / close valves (AV1), (AV)
2), ... And each open / close valve (AV1), (AV
2), ... By switching between open and close, the compressor (4),
It is assumed that the flow rate of the refrigerant from (8) to the refrigerant tank (Th) is adjusted.

The invention of claim 4 or 5 is an operation control method of a refrigerator for a linear motor car.

That is, according to the invention of claim 4,
In the same manner as in the above invention, the compressors (4) and (8) and the expansion means (3) are placed in a refrigerant tank (Th) that stores a liquid refrigerant that cools and holds the superconducting magnet of the linear motor car at a critical temperature or lower.
Part of the refrigerant circuit having 8) is opened, and the gas refrigerant evaporated in the refrigerant tank (Th) is drawn into the refrigerant circuit and compressed by the compressors (4) and (8), and then expanded by the expansion means (38). As an operation control method of the linear motor car refrigerator in which the refrigerant is expanded and a liquid refrigerant is generated by the temperature drop due to the expansion and returned to the inside of the refrigerant tank (Th), when the demagnetization of the superconducting magnet is performed, the compressor ( 4) The refrigerant flow rate from (8) to the refrigerant tank (Th) is switched from the normal flow rate to 0, and when the demagnetization is completed, the refrigerant flow rate is switched to the set flow rate lower than the normal flow rate and then returned to the normal flow rate. Characterize.

Further, in the fifth aspect of the invention, as in the second aspect of the invention, when the superconducting magnet is demagnetized, the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th) is changed. When the normal flow rate is switched to the first set flow rate lower than the normal flow rate and the excitation / demagnetization is completed, the refrigerant flow rate is switched to the second set flow rate lower than the normal flow rate and higher than the first set flow rate, and then to the normal flow rate. It is designed to be returned.

[0021]

With the above structure, in the invention of claim 1 or 4, when the superconducting magnet of the linear motor car is demagnetized,
This is detected by the excitation / demagnetization operation detecting means (53), and the refrigerant flow rate adjusting means (19) is controlled by the control means (54) receiving the output signal of the detecting means (53),
During the excitation / demagnetization of the superconducting magnet, the flow rate of the refrigerant reaching the refrigerant tank (Th) is switched from the normal flow rate to zero. Then, when the refrigerant flow rate is returned to the normal flow rate after the excitation / demagnetization of the superconducting magnet is completed, the refrigerant flow rate is once switched to the set flow rate lower than the normal flow rate and then returned to the normal flow rate. In this way, after the superconducting magnet is demagnetized, the refrigerant flow rate is returned to the normal flow rate via the set flow rate. Therefore, while the flow rate is at the set flow rate, the refrigerant tank (Th) is removed from the compressors (4) and (8). The pressure of the refrigerant reaching the point (1) decreases and the flow rate decreases, which can effectively prevent the internal pressure of the refrigerant tank (Th) from rising above the peak value during demagnetization.

Further, in the invention of claim 2 or 5, when the superconducting magnet of the linear motor car is excited and demagnetized, this is detected by the excitation / demagnetization operation detection means (53), as in the above. The control means (54) receiving the output signal of (1) controls the refrigerant flow rate adjusting means (19). During the demagnetization of the superconducting magnet, the refrigerant tank (T
After the demagnetization is completed, the refrigerant flow rate up to (h) is switched from the normal flow rate to the first set flow rate, and then the refrigerant flow rate is switched to the second set flow rate higher than the first set flow rate, and then returned to the normal flow rate. Be done. Even in this case, the refrigerant flow rate is the first
The refrigerant pressure from the compressors (4) and (8) to the refrigerant tank (Th) decreases while the flow rate is set, and the refrigerant tank (T
It is possible to effectively suppress the increase of the internal pressure in h) exceeding the peak value during demagnetization.

According to the third aspect of the invention, when the refrigerant flow rate adjusting means (19) adjusts the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), the compressors (4) and (8). ) To the refrigerant tank (Th), a plurality of branch pipes (15a), (15) in the middle of the refrigerant pipe (15).
b), ... The on-off valves (AV1) respectively arranged in
When one of (AV2), ... Is opened, this on-off valve (AV
Branch pipes (15a) corresponding to 1), (AV2), ...
The refrigerant is supplied to the refrigerant tank (Th) via (15b), .... These branch pipes (15a), (15b),
... are throttle valves (V1), (V2), which have different opening degrees,
... are arranged, each on-off valve (AV1), (AV
2), ... By switching between open and close, the compressor (4),
The flow rate of the refrigerant from (8) to the refrigerant tank (Th) can be adjusted, so that the desired configuration of the refrigerant flow rate adjusting means (19) can be easily obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.

(Embodiment 1) FIG. 4 shows the entire structure of a refrigerator (R) for a linear motor car according to Embodiment 1 of the present invention.
This refrigerator (R) is for cooling a superconducting coil (not shown) of a superconducting magnet included in a linear motor car with liquid helium (refrigerant), and a liquid helium tank (Th) for storing liquid helium. The superconducting coil of the superconducting magnet is immersed in the helium tank (Th) and stored in the helium tank (Th).
The liquid helium cools and holds the superconducting coil below the critical temperature.

The refrigerator (R) includes a compressor unit (1) and a refrigerator unit (2) arranged in a vacuum dewar (D).
It consists of 1) and. In the compressor unit (1), a low-frequency helium gas from the low-pressure gas suction port (2) is sucked in through the low-pressure pipe (3) and compressed, and a variable operating frequency inverter type JT compressor (4) is used. A heat exchanger (5) for cooling the helium gas discharged from the JT compressor (4), and a helium gas discharged from the heat exchanger (5) at an intermediate pressure gas inlet ( 6) An inverter type precooling compressor (8) with variable operating frequency for compressing to a higher pressure together with the intermediate pressure helium gas sucked from 6) through the intermediate pressure pipe (7), and the precooling compressor (8) A pre-stage oil separator (9) for separating oil for compressor lubrication from the discharged high-pressure helium gas, and a heat exchanger (1) for cooling the high-pressure helium gas discharged from the pre-stage oil separator (9).
0) and the latter-stage oil separator (1) for further separating lubricating oil from the helium gas discharged from the heat exchanger (10).
1) and an adsorber (12) for adsorbing and removing impurities from the helium gas discharged from the latter-stage oil separator (11) are arranged, and the discharge side of the adsorber (12) is a high-pressure pipe for precooling ( 13) to the precooling high-pressure gas discharge port (14), and the JT high-pressure gas discharge port (14) branched from the pre-cooling high-pressure pipe (13). 1
6), respectively.

The JT high-pressure pipe (15) is branched in parallel to the first and second branch pipes (15a) and (15b) on the way, and the flow rate is adjusted to the first branch pipe (15a). Fixed throttle-type first throttle valve (V1) and a pneumatic first type throttle valve (V1) on the high-pressure gas discharge port (16) side.
An on-off valve (AV1) is provided. On the other hand, the same second throttle valve (V2) and second open / close valve (AV2) are arranged in the second branch pipe (15b), and the second throttle valve (V2) is provided.
The opening degree of is smaller than that of the first throttle valve (V1).

In this embodiment, two JT high-pressure pipes (15) from the precooling compressor (8) to the liquid helium tank (Th) are branched in parallel to form two branch pipes (15a), (15b) and the branch pipes (15a),
Throttle valves (V1) and (V2), which are respectively disposed in (15b) and have different opening degrees, and branch pipes (15a),
Open / close valves (AV1) and (A) for opening and closing (15b) respectively.
V2) and a refrigerant flow rate adjusting mechanism (19) are configured, and each on-off valve (A) of the refrigerant flow rate adjusting mechanism (19) is configured.
By opening and closing V1) and (AV2), the helium gas flow rate from the compressor (8) to the liquid helium tank (Th) is adjusted.

Further, one end of a helium gas supply / discharge pipe (17) is branched and connected to the low pressure pipe (3) between the suction side of the JT compressor (4) and the low pressure gas suction port (2). Is
The other end of the helium gas supply / discharge pipe (17) has a buffer tank (T) for storing the helium gas at a predetermined pressure (PB).
connected to b). Helium gas supply and discharge piping (17)
Is branched in parallel to two branch pipes (17a) and (17b), and one of the branch pipes (17a) has a fixed throttle valve (VA1) for adjusting the flow rate and the throttle valve (VA).
The first low-pressure control valve (LPR1) on the low-pressure pipe (3) side of 1)
While the other branch pipe (17b) is provided with a similar throttle valve (VA2) and a second low pressure control valve (LPR).
2) and are provided. Each low pressure control valve (LPR
1) and (LPR2) automatically open as a pilot pressure when the pressure of the helium gas in the low-pressure pipe (3) (internal pressure of the liquid helium tank (Th)) drops below a set pressure, This low pressure control valve (LPR1), (LP
With the opening of R2), the helium gas in the buffer tank (Tb) is supplied to the low pressure pipe (3) (refrigerant circuit).

In the JT high-pressure pipe (15), a second branch pipe (15b) in which a second throttle valve (V2) is arranged, and a collecting portion of the helium gas supply / discharge pipe (17). Are connected by a helium gas return pipe (18) in which a high pressure control valve (HPR) is arranged. The high pressure control valve (HPR) automatically opens as a pilot pressure when the pressure of the helium gas in the JT high pressure pipe (15) rises above a set pressure. H
By opening the valve (PR), the helium gas in the JT high-pressure pipe (15) (refrigerant circuit) is returned to the buffer tank (Tb).

On the other hand, the refrigerator unit (21)
Includes a pre-cooling refrigerator (22) (expander) connected to the pre-cooling compressor (8) of the compressor unit (1) in a closed circuit.
And a J-T refrigerator (31) connected in series with the J-T compressor (4) and the pre-cooling compressor (8). The pre-cooling refrigerator (22) comprises a GM (Gifford McMahon) cycle refrigerator,
Helium gas is compressed and expanded to precool the helium gas (refrigerant gas) in the JT refrigerator (31). This pre-cooling refrigerator (22) is the above vacuum dewar (D).
And a cylinder (24) having a large and small two-stage structure connected to the case (23). The case (23) has a high pressure gas inlet (26) connected to the high pressure gas discharge port (14) for precooling of the compressor unit (1) through a flexible pipe (25), and an intermediate pressure gas suction port. Low pressure gas outlet (2) connected to (6) via flexible piping (27)
8) and are opened. On the other hand, the cylinder (24) penetrates the side wall of the vacuum dewar (D) and extends to the inside thereof, and the tip of the large diameter portion (24a) thereof is cooled and maintained at a predetermined temperature level in the first heat station (29). ) And the tip of the small diameter portion (24b) is formed in the second heat station (30) which is cooled and held at a temperature level lower than that of the first heat station (29).

That is, although not shown here, in the cylinder (24), each of the heat stations (2
Free type displacers (replacers) that partition and form expansion spaces are reciprocally fitted at positions corresponding to 9) and (30). On the other hand, the above case (2
In 3), a rotary valve that opens and closes each time it rotates,
A valve motor that drives the rotary valve is housed. The rotary valve has the high pressure gas inlet (26).
The helium gas flowing in from is supplied to each expansion space in the cylinder (24), or the helium gas expanded in each expansion space is switched to be discharged from the low pressure gas outlet (28). Then, by opening and closing this rotary valve, the high-pressure helium gas is expanded by Simon in each expansion space in the cylinder (24), and a temperature drop due to the expansion causes a cryogenic level of cold to be generated, and the cold is cooled by the cylinder (24). First and second heat stations (29), (3
Hold at 0). That is, in the pre-cooling refrigerator (22),
The high-pressure helium gas discharged from the pre-cooling compressor (8) is adiabatically expanded to heat stations (29), (3).
0) to lower the temperature to precool later-described precoolers (36) and (37) in the J-T refrigerator (31),
The expanded low pressure helium gas is returned to the compressor (8) and recompressed.

On the other hand, the JT refrigerator (31) has about 4
A refrigerator that expands helium gas by Joule-Thomson to generate K-level coldness, the refrigerator (31) being a first refrigerator arranged in the vacuum dewar (D).
-The 3rd JT heat exchanger (32)-(34) is provided. Each of the J-T heat exchangers (32) to (34) exchanges heat between the helium gases passing through the primary side and the secondary side, respectively.
The secondary side is connected to the JT high-pressure gas discharge port (16) of the compressor unit (1) via a flexible pipe (35). In addition, the first and second JT heat exchangers (3
The primary side of each of 2) and (33) is connected to the pre-cooling refrigerator (2
It is connected via a first precooler (36) arranged on the outer periphery of the first heat station (29) of the cylinder (24) in (2). Similarly, the respective primary sides of the second and third J-T heat exchangers (33), (34) are connected via the second precooler (37) arranged on the outer periphery of the second heat station (30). Has been done. Further, the primary side of the third J-T heat exchanger (34) is connected to a J-T valve (38) for expanding the high-pressure helium gas into the adsorber (3).
9). The opening of the JT valve (38) is adjusted from the outside of the vacuum dewar (D) by the operation rod (38a). The JT valve (38) is a liquid helium return pipe (40) made of a stainless steel pipe.
Through the helium tank (Th).
The inside of the helium tank (Th) is connected to the secondary side of the third JT heat exchanger (34) through a helium gas suction pipe (41) made of the same stainless steel pipe. And, 2 of this 3rd J-T heat exchanger (34)
The secondary side goes through the secondary side of the second JT heat exchanger (33) to the first side.
It is connected to the secondary side of the JT heat exchanger (32) and
The secondary side of the JT heat exchanger (32) is connected to the low pressure gas inlet (2) of the compressor unit (1) via a flexible pipe (42).

That is, the JT refrigerator (31) includes flexible pipes (35) and (42), low pressure pipe (3), both compressors (4) and (8), and JT high pressure pipe (15). To the helium tank (Th) through a liquid helium return pipe (40) and a helium gas suction pipe (41). Helium gas evaporated in (Th) is sucked into the refrigerant circuit from the gas suction pipe (41) and passed through each of the secondary sides of the third to first J-T heat exchangers (34) to (32) for JT and The pre-cooling compressors (4) and (8) are sucked and compressed. Further, the high pressure helium gas compressed by the precooling compressor (8) is supplied to the compressor (4) side at low temperature and low pressure in the first to third JT heat exchangers (32) to (34). Heat exchange with helium gas and first
And the second precoolers (36) and (37) respectively for the first and second heat stations (29) of the cylinder (24),
After cooling at (30), the JT valve (38)
Expanded Thomson into helium in a liquid state of about 4K,
The liquid helium is returned to the tank (Th) via the liquid helium return pipe (40).

The first and second on-off valves (AV1), (A
V2) is connected to a manifold unit (52) that receives a control signal from a power supply control unit (51) that controls the operating frequencies of the compressors (4) and (8) and switches the action or suspension of air pressure. . The power supply control unit (51) includes a high pressure sensor (HP) for detecting the pressure of the high pressure helium gas discharged from the precooling compressor (8).
S), the detection signal of the low pressure sensor (LPS) for detecting the pressure of the low pressure helium gas in the low pressure pipe (3) communicating with the suction side of the JT compressor (4), and the helium gas supply. Pressure in the drain pipe (17) (buffer tank (Tb)
The detection signal of the buffer tank pressure sensor (MPS) that detects the internal pressure (PB) of the compressor and the operation signals of the three protection switches (SS1) to (SS3) in the compressor unit (1) are input.

The control operation performed by the power supply control unit (51) will be described with reference to FIGS. 2 and 3. First, in step ST1, it is determined whether to switch manually or automatically,
When this judgment is manual, after the operation button is turned ON in step ST2, when it is automatic, in step ST2
After inputting the external operation signal in step 3,
Proceed to T4. In step ST4, it is determined whether the operation mode is switched. If the determination is in the low speed mode, the operation frequency f of the compressors (4) and (8) is set to, for example, f = 40 Hz in step ST5, and the first opening / closing valve ( After opening AV1) and closing the second on-off valve (AV2), the protection switch (SS) of the compressor unit (1) is opened at step ST6.
It is determined whether 1) to (SS3) are activated. When this determination is YES, after displaying an abnormal state in step ST22, the process proceeds to step ST23, and the compressors (4) and (8) are stopped. Then, step ST2
In step 4, the first on-off valve (AV1) is closed to stop the operation.

When the determination in step ST6 is NO, the low speed operation is executed in step ST7, the stop button is turned on in step ST21, and then the process proceeds to step ST23.

When the determination in step ST4 is in the normal mode, the operating frequency f of the compressors (4) and (8) is set to, for example, f = 55 Hz in step ST8, and the first opening / closing valve (AV1) is opened. After closing the second on-off valve (AV2), the process proceeds to step ST9, and similarly to step ST6, the protection switch (SS1) of the compressor unit (1).
~ (SS3) determines whether or not activated. If the determination is YES, the process proceeds to step ST22, but if the determination is NO, the buffer tank pressure (PB
) Is lower than 3.0 kg / cm ^2, for example, and if the determination is NO at PB ≧ 3.0, the normal operation is executed in step ST20, and then the process proceeds to step ST21. YES in step ST10
In case of, the low speed operation is executed in step ST11,
At step ST12, it is determined whether or not the buffer tank pressure (PB) is higher than 4.0 kg / cm ^2, for example, and if the determination is NO at PB ≤4.0, the above step S12 is performed.
Return to T11, but if YES, go to step ST2
Go to 0.

Further, when the determination in step ST4 is in the excitation / demagnetization mode, the operating frequency f of the compressors (4) and (8) is set to, for example, f = 70 Hz in step ST13, and the first and second opening / closing valves ( After closing both AV1) and (AV2), the process proceeds to step ST14, and it is determined whether or not the protection switches (SS1) to (SS3) of the compressor unit (1) have been actuated, as in step ST6. If the determination is YES, the process proceeds to step ST22, but if the determination is NO, the process proceeds to step ST15 to execute the demagnetization of the superconducting magnet. Then, step ST16
It is determined whether or not the excitation / demagnetization has ended. If this determination is NO, the process returns to step ST15, but if the determination is YES, then in step ST17 the first set time (T1)
It is determined whether (for example, T1 = 60 seconds) has elapsed. When this judgment is NO, the same step ST17 is repeated, but when the judgment is YES, the routine proceeds to step ST18, where the first on-off valve (AV1) is closed as it is, and the second
After opening only the on-off valve (AV2), step ST1
9 and proceed to the second set time (T2) (for example, T2 = 20
Second) has elapsed. When this determination is NO, steps ST18 and ST19 are repeated, but when the determination is YES, the process proceeds to step ST20.

In this embodiment, the step ST4 constitutes an excitation / demagnetization operation detection means (53) for detecting the excitation / demagnetization of the superconducting magnet in the linear motor car.

Further, steps ST13, ST15 to ST
20 receives the output signal of the excitation / demagnetization operation detection means (53), and during the excitation / demagnetization of the superconducting magnet, both the first and second on-off valves (AV1), (AV2) are closed to close the precooling compressor ( When the helium gas flow rate from 8) to the liquid helium tank (Th) is switched from the normal flow rate to 0 and the first set time (T1) elapses after the superconducting magnet has been demagnetized, the second set time (T2) elapses. Until then, only the second opening / closing valve (AV2) is opened to switch the helium gas flow rate to a set flow rate that is lower than the normal flow rate, and then only the first opening / closing valve (AV1) is opened to set the helium gas flow rate to the normal flow rate. A control means (54) is configured to control the refrigerant flow rate adjusting mechanism (19) so as to return it.

Next, the operation of the above embodiment will be described. In the steady state in which the superconducting magnet of the linear motor car is operated, the superconducting coil of the superconducting magnet is cooled and maintained below the critical temperature by the liquid helium in the helium tank (Th). Further, the helium gas evaporated in the helium tank (Th) is sucked from the helium gas suction pipe (41) opening in the tank (Th) and supplied to the refrigerant circuit of the refrigerator (R), where it is compressed and compressed. It is cooled by expansion and liquefied. The liquid helium is returned to the tank (Th) through the liquid helium return pipe (40). As a result, a predetermined amount or more of liquid helium is stored in the tank (Th), and the superconducting coil is stably cooled below the critical temperature.

The operation of the refrigerator (R) will be described in more detail. In the steady operation state, a part of the high-pressure helium gas supplied from the precooling compressor (8) of the compressor unit (1) is precooled. The first heat station (29) expands in each expansion space in the cylinder (24) of the refrigerator (22) (expander), and the first heat station (29) reaches a predetermined temperature level due to the temperature drop accompanying the expansion of the gas, and the second heat station. (30) are each cooled to a lower temperature level than the first heat station (29). The helium gas expanded in the expansion space returns to the compressor unit (1) and is sucked into the precooling compressor (8) via the intermediate pressure pipe (7) and compressed.

On the other hand, J- in the compressor unit (1)
The first on-off valve (AV1) of the T high-pressure pipe (15) is opened while the second on-off valve (AV2) is closed, so that the high-pressure helium gas discharged from the precooling compressor (8) is discharged. The remainder enters the primary side of the first JT heat exchanger (32) of the JT refrigerator (31) via the first throttle valve (V1) of the JT high pressure pipe (15), Then, heat is exchanged with the low pressure helium gas on the secondary side toward the compressor (4) side, and the temperature is kept at room temperature 300.
It is cooled from K to about 50K, and thereafter, it is further cooled by entering the first heat station (29) of the precooling refrigerator (22) and the first precooler (36) on the outer periphery. This cooled gas enters the primary side of the second J-T heat exchanger (33) and is cooled to about 15 K by heat exchange with the low pressure helium gas on the secondary side as well, and then the precooling refrigerator ( 22) second heat station (30) outer peripheral second precooler (3
It goes into 7) and is cooled further. After this, the gas is the 3rd J
It enters the primary side of the -T heat exchanger (34) and is further cooled by heat exchange with the low pressure helium gas on the secondary side before reaching the JT valve (38). In this JT valve (38), the high-pressure helium gas is throttled and expanded by Joule-Thomson into liquid helium of about 4K, and this liquid helium passes through the liquid helium return pipe (40) to the tank (Th). Is supplied to. Further, the helium gas evaporated in the tank (Th) is sucked into the secondary side of the third J-T heat exchanger (34) through the helium gas suction pipe (41), and the second and first J-T heats are absorbed. It is sucked into the JT compressor (4) via the secondary sides of the exchangers (33) and (32) and compressed.

When demagnetization for stopping the generation of the magnetic field by the superconducting magnet or excitation by applying a current is performed for maintenance or inspection of the linear motor car, as shown in FIG. The machine (R) is in the excitation / demagnetization mode, and each compressor (4) in the refrigerator (R),
The operating frequency f of (8) rises from f = 55 Hz to 70 Hz, and as a result, the suction amount of the evaporated helium gas in the liquid helium tank (Th) to the JT compressors (4) and (8), that is, The outflow amount of the evaporated helium gas from the tank (Th) increases. Also, the J-T of the compressor unit (1)
The second on-off valve (AV2) in the high-pressure pipe (15) is closed as it is, but the first (AV1) is switched from the open state to the closed state.
By closing the valve V2), the JT high-pressure pipe (15) is closed, and the amount of helium flowing into the liquid helium tank (Th) becomes zero. That is, while the outflow amount of the evaporated helium gas from the liquid helium tank (Th) increases, the inflow amount is 0
Therefore, the internal pressure decreases, and in this state, the demagnetization of the superconducting magnet of the linear motor car is executed. Therefore, even if the heat load increases due to the execution of the demagnetization of the superconducting magnet, the rise of the internal pressure of the liquid helium tank (Th) is suppressed, so that the safety valve can be prevented from operating.

When the excitation / demagnetization of the superconducting magnet is completed and the first set time (T1) elapses thereafter, the first on-off valve (A
V1) is maintained in the closed state as it is, but the second opening / closing valve (AV2) is opened, whereby the high-pressure helium gas flows through the second throttle valve (V2) of the JT high-pressure pipe (15). Enter via liquid helium tank (Th). Since the opening degree of the second throttle valve (V2) is smaller than that of the first throttle valve (V1), the flow rate of helium gas supplied to the liquid helium tank (Th) is maintained at a set flow rate lower than the normal flow rate.
After that, when the second set time (T2) elapses, only the first opening / closing valve (AV1) is opened and the helium gas flow rate is returned to the normal flow rate as before.

That is, in this embodiment, when the helium gas flow rate is returned to the normal flow rate determined by the opening degree of the first throttle valve (V1) after the demagnetization of the superconducting magnet of the linear motor car is completed, first, the helium gas flow rate is set. Is switched to a set flow rate (flow rate determined by the opening degree of the second throttle valve (V2)) that is smaller than the normal flow rate, and then returned to the normal flow rate. Therefore, while this flow rate is at the set flow rate, the liquid is discharged from the compressor (8). The flow rate of the helium gas reaching the helium tank (Th) can be reduced by lowering the pressure thereof. As a result, as shown in FIG. 6, it is possible to effectively prevent the internal pressure of the liquid helium tank (Th) from rising beyond the peak value during demagnetization as in the conventional case, and the demagnetization mode of the refrigerator (R). Driving time can be shortened. As a result, the compressor (4),
The time for raising the operating frequency of (8) is short, and the durability can be improved. In addition, refrigerator (R)
Since the operating time of the excitation / demagnetization mode is short, the flow rate balance between the helium gas directed to the liquid helium gas (Th) and the helium gas returned from the tank (Th) to the compressor (4) in the JT side refrigerant circuit There is no fear that the temperature of the suction gas to the compressor will drop due to the collapse of the frost and the frost will adhere to the flexible pipe (42). Also, liquid helium tank (T
The evaporation amount of helium gas in h) can be reduced, and further, the recovery amount of helium gas in the buffer tank (Tb) can be reduced.

(Embodiment 2) FIGS. 7 to 10 show Embodiment 2 (note that the same parts as those in FIGS. 2 to 5 are designated by the same reference numerals and detailed description thereof will be omitted), In No. 1, the flow rate of the helium gas is set to 0 for the demagnetization of the superconducting magnet, whereas a predetermined flow rate is made to flow.

That is, in this embodiment, as shown in FIG. 9, the JT high-pressure pipe (15) in the compressor unit (1) is provided with three branch pipes (15) (1 to 3) on the way.
a) to (15b) are branched in parallel, and the first branch pipe (1
5a) is a fixed first throttle valve (V
1) and a pneumatic first on-off valve (AV1) are provided. A similar second throttle valve (V
2) and the second on-off valve (AV2), and the third branch pipe (15c) is also provided with the same third throttle valve (V3) and third on-off valve (AV3). Comparing the opening degrees of these three throttle valves (V1) to (V3), the opening degree of the second throttle valve (V2) is the smallest, and then the third throttle valve (V3) and the first throttle valve (V1). The opening is set to be large in order.

The control operation of the power supply control unit (51) is basically the same as that of the first embodiment (see FIGS. 2 and 3), except for the following parts. That is, as shown in FIGS. 7 and 8, first, when the determination in step ST4 is the excitation / demagnetization mode, in step ST13, the compressor (4),
The operating frequency f of (8) is set to, for example, f = 70 Hz,
After closing both the first and third opening / closing valves (AV1) and (AV3) and opening only the second opening / closing valve (AV2),
It proceeds to step ST14.

In step ST18, the first on-off valve (AV1) is closed, the second on-off valve (AV2) is switched from the open state to the closed state, and the third on-off valve (A) is opened.
After opening V3), the process proceeds to step ST19.

Further, during the steady operation of step ST20, only the first opening / closing valve (AV1) is opened.

Therefore, in this embodiment, the control means (54) is constituted by the steps ST13, ST15 to ST20 of the flow shown in FIG. 7 and FIG.
4) receives the output signal of the excitation / demagnetization operation detection means (53), and during the excitation / demagnetization of the superconducting magnet, the first and third on-off valves (A).
Both V1) and (AV3) are closed and the second on-off valve (AV
2) only open the helium gas flow rate from the precooling compressor (8) to the liquid helium tank (Th) from the normal flow rate set by the first throttle valve (V1) to the second throttle valve (V).
After switching to the first set flow rate set in 2) and ending the demagnetization of the superconducting magnet, the first set time (T1) passes,
Until the second set time (T2) elapses, only the third opening / closing valve (AV3) is opened so that the helium gas flow rate is lower than the normal flow rate and higher than the first set flow rate (third throttle). The flow rate is set to the value set by the valve (V3), and then only the first opening / closing valve (AV1) is opened to control the refrigerant flow rate adjusting mechanism (19) so as to return the helium gas flow rate to the normal flow rate.

Therefore, in the case of this embodiment, as shown in FIG. 10, in the operating state of the superconducting magnet in the linear motor car, only the first opening / closing valve (AV1) of the JT high-pressure pipe (15) is opened. The helium gas flow rate is set to the normal flow rate. And when the superconducting magnet is demagnetized,
During the execution, only the second opening / closing valve (AV2) of the JT high-pressure pipe (15) is opened to set the flow rate of helium gas to the first set flow rate. This excitation / demagnetization ends, and then the first
When the set time (T1) has elapsed, the second opening / closing valve (AV2)
Is closed and the third on-off valve (AV3) is opened instead, so that high-pressure helium gas is passed through the third throttle valve (V3) of the JT high-pressure pipe (15) to the liquid helium tank. (Th) is entered, and the flow rate of the helium gas at that time is the second set flow rate set by the third throttle valve (V3). Further, when the second set time (T2) elapses thereafter, only the first opening / closing valve (AV1) is opened and the helium gas flow rate is returned to the original normal flow rate. Therefore, also in this embodiment, the same operational effect as that of the above-described first embodiment can be obtained.

In each of the above embodiments, the JT high-pressure pipe (15) is provided with a plurality of branch pipes (15a), (15b), ...
To the branch pipes (15a), (15b), ...
The flow rate of the helium gas is adjusted by switching the open / close valves (AV1), (AV2), ...
It is also possible to perform the same flow rate adjustment by combining (AV2), ... And controlling the opening and closing. Also, J-T
It is also possible to use one pneumatic high-pressure pipe (15) and use a pneumatic proportional control valve whose opening is variable, and the same effect can be obtained.

[0056]

As described above, according to the first or fourth aspect of the invention, the refrigerant circuit is opened in the tank for storing the liquefied refrigerant that cools and holds the superconducting magnet of the linear motor car below the critical temperature, and vaporizes in the tank. The refrigerant gas is taken into the refrigerant circuit, cooled and reliquefied by compression and expansion, and the liquefied refrigerant is returned to the inside of the cryogenic refrigerator, and the refrigerant flow rate from the compressor to the refrigerant tank is adjusted. When the refrigerant flow rate adjusting means is provided to perform the demagnetization of the superconducting magnet, the refrigerant flow rate from the compressor to the refrigerant tank is set to 0 during execution, and when the refrigerant flow rate is returned to the normal flow rate after the end of the demagnetization. The flow rate was once returned to the normal flow rate after switching to the set flow rate lower than the normal flow rate. Further, in the invention of claim 2 or 5, during the execution of the demagnetization of the superconducting magnet,
When the refrigerant flow rate from the compressor to the refrigerant tank is set to the first set flow rate which is lower than the normal flow rate and the refrigerant flow rate is returned to the normal flow rate after the end of the demagnetization, once the flow rate is lower than the normal flow rate and higher than the first set flow rate. 2 After switching to the set flow rate, the normal flow rate was restored. Therefore, according to these inventions, when the refrigerant flow rate is returned to the normal flow rate after the demagnetization of the superconducting magnet in the linear motor car, the pressure of the refrigerant from the compressor to the refrigerant tank is reduced while the flow rate is at the intermediate set flow rate. It is possible to reduce the flow rate and effectively suppress the rise of the internal pressure of the refrigerant tank beyond the peak value during excitation / demagnetization, shorten the operating time of the refrigerator demagnetization operation mode, and It is possible to improve durability, prevent frost on the connection pipe, reduce the amount of refrigerant evaporated in the tank, and reduce the amount of refrigerant collected in the buffer tank.

According to the third aspect of the present invention, a plurality of branch pipes are formed by branching the refrigerant pipes from the compressor to the refrigerant tank in parallel, and throttle valves that are arranged in the respective branch pipes and have different opening degrees. An opening / closing valve for opening / closing each branch pipe is provided, and each opening / closing valve is opened / closed to adjust the refrigerant flow rate from the compressor to the refrigerant tank, thereby facilitating a desirable configuration of the refrigerant flow rate adjusting means. Can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a flowchart showing the first half of the control operation performed by the power supply control unit according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the latter half of the control operation performed by the power supply control unit.

FIG. 4 is a refrigerant circuit diagram showing the overall configuration of a refrigerator for a linear motor car in the first embodiment.

FIG. 5 is a time chart showing switching between opening and closing of the on-off valve and changes in the helium gas flow rate associated therewith in the first embodiment.

FIG. 6 is a characteristic diagram showing changes in the internal pressure of the liquid helium tank when the superconducting magnet is excited and demagnetized in Example 1.

FIG. 7 is a view corresponding to FIG. 2 showing a second embodiment.

FIG. 8 is a view corresponding to FIG. 3 showing a second embodiment.

9 is a view corresponding to FIG. 4 showing the second embodiment.

10 is a view corresponding to FIG. 5 showing the second embodiment.

[Explanation of symbols]

 (R) Refrigerator (1) Compressor unit (4), (8) Compressor (15) JT high-pressure pipe (refrigerant pipe) (15a), (15b), (15c) Branch pipe (AV1), (AV2), (AV3) Open / close valves (V1), (V2), (V3) Throttle valve (19) Refrigerant flow rate adjusting mechanism (refrigerant flow rate adjusting means) (21) Refrigerator unit (22) Pre-cooling refrigerator (31) J-T refrigerator (38) J-T valve (expansion means) (51) Power supply control unit (53) Excitation / demagnetization operation detection means (54) Control means (Th) Liquid helium tank (refrigerant tank) (Tb) Buffer tank

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[Procedure amendment]

[Submission date] November 9, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Refrigerator operation control device and operation control method

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is attached to a refrigerant tank for storing a liquefied refrigerant for cooling a superconducting magnet such as a linear motor car to a cryogenic temperature level, and a refrigerant gas evaporated in the refrigerant tank is attached to the refrigerant tank. The present invention relates to an operation control device and an operation control method for a refrigerator that is sucked into a refrigerant circuit, liquefied by compression and expansion, and returned to the inside of a tank.

[0002]

2. Description of the Related Art In recent years, for example, a linear motor car having a superconducting magnet has attracted attention. In this superconducting magnet, liquid helium stored in the tank is used to cool and maintain the superconductor used for the coil below the critical temperature, but since this liquid helium evaporates in the tank,
It is necessary to cool and condense the evaporated helium gas to liquefy it, and a cryogenic refrigerator is used for this purpose.

As an example of a refrigerator for cooling the helium gas to a condensing temperature, there is a conventional one, for example, US Pat. No. 4,223.
No. 540, etc., a pre-cooling refrigerator and a J-
There is a refrigerator combined with a T refrigerator. The above pre-cooling refrigerator is a GM cycle (Gifford McMahon cycle)
And a refrigerating machine such as an improved solve cycle. The helium gas (refrigerant gas) compressed by the compressor is adiabatically expanded by the expander, and the temperature drop of the gas causes the cryogenic cold level at the heat station. .

On the other hand, the JT refrigerator has a precooler for precooling by exchanging heat between the helium gas supplied from the compressor and the heat station of the expander in the precooling refrigerator, and the helium gas in a joule. Thomson inflates J-
It is connected with a T valve, and helium gas from the compressor is precooled by a precooler, and the precooled helium gas is expanded by Joule-Thomson with the JT valve to generate 4K level cold. It is like this.

When the evaporated helium gas in the tank is cooled by a refrigerator, two refrigerant pipes are arranged in the tank so that one end of each refrigerant pipe opens into the tank and the other end of both pipes is arranged. Is taken out of the tank and connected in series to the refrigerant circuit of the JT refrigerator, so that the inside of the tank becomes a part of the refrigerant circuit of the refrigerator, and the evaporated helium gas in the tank is JT frozen from one pipe. Sucked into the refrigerant circuit of the machine and compressed by the compressor, the compressed helium gas is expanded by the JT valve to be cooled and liquefied, and this liquid helium is returned to the tank through the other pipe. Has been done.

By the way, the internal pressure of the liquid helium tank for cooling the superconducting magnet of a linear motor car or the like to a critical temperature or lower is within a predetermined range (0.15) during normal operation of the refrigerator.
It is balanced at about 0.25 kg / cm ² G).
However, when demagnetization for stopping the generation of the magnetic field by the superconducting magnet or excitation by applying a current from the outside is performed for maintenance or inspection of the linear motor car or the like, the heat load increases and the pressure in the tank rises. When the tank internal pressure exceeds the upper limit value (for example, 0.4 kg / cm ² G), the safety valve operates to evaporate the helium gas in the tank to the outside of the tank.

In order to avoid the operation of this safety valve, conventionally,
When performing the demagnetization of the superconducting magnet, the operating frequency of the compressor in the JT refrigerator is increased to increase the suction amount of the helium gas sucked from the liquid helium tank into the compressor, and the refrigerant of the JT refrigerator. Operate the refrigerator in an excitation / demagnetization mode that temporarily reduces the gas flow rate in the circuit to 0 or lowers it from the normal flow rate (gas flow rate during normal operation of the superconducting magnet) to reduce the gas flow rate into the tank. As a result, the tank internal pressure is reduced and the difference from the suction amount into the compressor is stored in the buffer tank.

[0008]

When the excitation / demagnetization of the superconducting magnet is performed in this manner, the rise in the tank internal pressure can be effectively suppressed as the gas flow rate decreases. However, when the gas flow rate is returned to the normal flow rate after the excitation / demagnetization, the helium gas rapidly returns to the inside of the tank, so that the tank internal pressure may rise again to a level exceeding the peak pressure accompanying the excitation / demagnetization.

In order to suppress the re-rise of the tank internal pressure to a low level, it is necessary to continuously operate the refrigerator in the excitation / demagnetization mode after the demagnetization of the superconducting magnet is completed until the tank internal pressure is reduced to some extent. However, in that case, the operating frequency of the compressor is kept high for a long period of time due to long-term excitation / demagnetization mode operation, and its durability decreases, and the flow rate balance between reciprocating gases in the refrigerant circuit is reduced. Collapse and the temperature of the return gas to the compressor decreases, frost is formed on the return side connecting pipe, the performance of the lubricating oil decreases due to the suction of low temperature helium gas of the compressor, and the performance of the liquid helium tank is reduced. This causes problems such as an increase in the amount of gas evaporation and an increase in the amount of helium recovered in the buffer tank.

The present invention has been made in view of the above points, and an object thereof is to effectively increase the internal pressure of the refrigerant tank by changing the operation control mode of the refrigerator after the demagnetization of the superconducting magnet. To try to suppress it.

[0011]

In order to achieve the above object, in the present invention, the refrigerant flow rate in the refrigerator is not returned to the normal flow rate at once after the end of the demagnetization of the superconducting magnet.
The flow was returned via an intermediate flow rate that is lower than the normal flow rate.

Specifically, in the invention of claim 1, as shown in FIG. 1, the compressor (4) is placed in a refrigerant tank (Th) for storing a liquid refrigerant for cooling and holding the superconducting magnet at a critical temperature or lower. , (8) and a part of the refrigerant circuit having the expansion means (38) are opened, and the gas refrigerant evaporated in the refrigerant tank (Th) is sucked into the refrigerant circuit and compressed by the compressors (4) and (8). After that, it is expanded by the expansion means (38), and the temperature drop due to the expansion generates a liquid refrigerant to generate a refrigerant tank (Th).
The premise is a refrigerator that can be put back inside.

A refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4), (8) to the refrigerant tank (Th) and an excitation for detecting that the superconducting magnet is demagnetized. Upon receiving the demagnetization operation detection means (53) and the output signal of the detection means (53), the refrigerant flow rate to the refrigerant tank (Th) is switched from the normal flow rate to 0 during the excitation / demagnetization of the superconducting magnet to end the excitation / demagnetization. After that, a control means (54) for controlling the refrigerant flow rate adjusting means (19) is provided so as to return the flow rate to the normal flow rate after switching the flow rate of the refrigerant to a set flow rate lower than the normal flow rate.

According to the second aspect of the present invention, when the superconducting magnet is excited and demagnetized, the refrigerant flow rate is set to a set flow rate other than 0, and after the end of the excitation and demagnetization, the refrigerant is changed from the set flow rate to the normal flow rate through a larger intermediate flow rate. I'm trying to bring it back.

That is, according to the present invention, as in the case of the first aspect of the present invention, the refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), An excitation / demagnetization operation detection means (53) for detecting the excitation / demagnetization of the superconducting magnet is provided.

Further, the refrigerant tank (Th) is received while the superconducting magnet is being demagnetized by receiving the output signal of the detecting means (53).
Is switched from the normal flow rate to the first set flow rate which is smaller than the normal flow rate, and after the completion of the demagnetization, the refrigerant flow rate is set to the second set flow rate which is lower than the normal flow rate and higher than the first set flow rate. Control means (5) for controlling the refrigerant flow rate adjusting means (19) so as to return to the normal flow rate after switching.
4) is provided.

In a third aspect of the invention, a desirable configuration of the refrigerant flow rate adjusting means is embodied. That is, in the present invention, the refrigerant flow rate adjusting means (19) includes the compressor (4),
Refrigerant piping (15) from (8) to the refrigerant tank (Th)
A plurality of branch pipes (15a), (1
5b), ... and the branch pipes (15a), (15b),
... and throttle valves (V
1), (V2), ... And each branch pipe (15a), (15
b), ... Open / close valves (AV1), (AV)
2), ... And each open / close valve (AV1), (AV
2), ... By switching between open and close, the compressor (4),
It is assumed that the flow rate of the refrigerant from (8) to the refrigerant tank (Th) is adjusted.

The invention of claim 4 or 5 is an operation control method of a refrigerator .

That is, according to the invention of claim 4,
Similarly to the invention of claim 1, an example of a refrigerant circuit having compressors (4), (8) and expansion means (38) in a refrigerant tank (Th) that stores a liquid refrigerant that cools and holds a superconducting magnet below a critical temperature. The part is opened, the gas refrigerant evaporated in the refrigerant tank (Th) is drawn into the refrigerant circuit, compressed by the compressors (4) and (8), and then expanded by the expansion means (38), and the temperature drop due to the expansion. A liquid refrigerant is generated by the refrigerant tank (Th)
As the operation control method of the refrigerating machine then returned within, when performing demagnetization of the superconducting magnet, the compressor (4),
The refrigerant flow rate from (8) to the refrigerant tank (Th) is switched from the normal flow rate to 0, and when the excitation / demagnetization is completed, the refrigerant flow rate is switched to a set flow rate lower than the normal flow rate and then returned to the normal flow rate. .

Further, in the fifth aspect of the invention, as in the second aspect of the invention, when the superconducting magnet is demagnetized, the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th) is changed. When the normal flow rate is switched to the first set flow rate lower than the normal flow rate and the excitation / demagnetization is completed, the refrigerant flow rate is switched to the second set flow rate lower than the normal flow rate and higher than the first set flow rate, and then to the normal flow rate. It is designed to be returned.

[0021]

With the above construction, in the invention of claim 1 or 4, when the superconducting magnet is demagnetized, that fact is detected by the excitation / demagnetization operation detecting means (53).
The refrigerant flow rate adjusting means (19) is controlled by the control means (54) receiving the output signal of 3), and the refrigerant flow rate to the refrigerant tank (Th) is reduced from the normal flow rate to 0 during the execution of the demagnetization of the superconducting magnet. Can be switched. When returning the refrigerant flow rate to the normal flow rate after the excitation / demagnetization of the superconducting magnet is completed,
The refrigerant flow rate is once switched to a set flow rate lower than the normal flow rate and then returned to the normal flow rate. In this way, after the superconducting magnet is demagnetized, the refrigerant flow rate is returned to the normal flow rate via the set flow rate. Therefore, while the flow rate is at the set flow rate, the refrigerant tank (Th) is removed from the compressors (4) and (8). The pressure of the refrigerant reaching the point (1) decreases and the flow rate decreases, which can effectively prevent the internal pressure of the refrigerant tank (Th) from rising above the peak value during demagnetization.

Further, in the invention of claim 2 or 5, when the superconducting magnet is excited and demagnetized, that is detected by the excitation and demagnetization operation detecting means (53), and the output of this detecting means (53) is the same as the above. The control means (54) receiving the signal controls the refrigerant flow rate adjusting means (19). During the excitation / demagnetization of the superconducting magnet, the refrigerant flow rate to the refrigerant tank (Th) is switched from the normal flow rate to the first set flow rate, and after the demagnetization is completed, the refrigerant flow rate is higher than the first set flow rate. Two
The flow rate is switched to the set flow rate and then returned to the normal flow rate. Even in this case, the pressure of the refrigerant from the compressors (4) and (8) to the refrigerant tank (Th) decreases while the refrigerant flow rate is at the first set flow rate, and the internal pressure of the refrigerant tank (Th) is being demagnetized. It is possible to effectively suppress the rise above the peak value of.

According to the third aspect of the invention, when the refrigerant flow rate adjusting means (19) adjusts the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), the compressors (4) and (8). ) To the refrigerant tank (Th), a plurality of branch pipes (15a), (15) in the middle of the refrigerant pipe (15).
b), ... The on-off valves (AV1) respectively arranged in
When one of (AV2), ... Is opened, this on-off valve (AV
Branch pipes (15a) corresponding to 1), (AV2), ...
The refrigerant is supplied to the refrigerant tank (Th) via (15b), .... These branch pipes (15a), (15b),
... are throttle valves (V1), (V2), which have different opening degrees,
... are arranged, each on-off valve (AV1), (AV
2), ... By switching between open and close, the compressor (4),
The flow rate of the refrigerant from (8) to the refrigerant tank (Th) can be adjusted, so that the desired configuration of the refrigerant flow rate adjusting means (19) can be easily obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.

(Embodiment 1) FIG. 4 shows the entire structure of a refrigerator (R) for a linear motor car according to Embodiment 1 of the present invention.
This refrigerator (R) is for cooling a superconducting coil (not shown) of a superconducting magnet included in a linear motor car with liquid helium (refrigerant), and a liquid helium tank (Th) for storing liquid helium. The superconducting coil of the superconducting magnet is immersed in the helium tank (Th) and stored in the helium tank (Th).
The liquid helium cools and holds the superconducting coil below the critical temperature.

The refrigerator (R) includes a compressor unit (1) and a refrigerator unit (2) arranged in a vacuum dewar (D).
It consists of 1) and. In the compressor unit (1), a low-frequency helium gas from the low-pressure gas suction port (2) is sucked in through the low-pressure pipe (3) and compressed, and a variable operating frequency inverter type JT compressor (4) is used. A heat exchanger (5) for cooling the helium gas discharged from the JT compressor (4), and a helium gas discharged from the heat exchanger (5) at an intermediate pressure gas inlet ( 6) An inverter type precooling compressor (8) with variable operating frequency for compressing to a higher pressure together with the intermediate pressure helium gas sucked from 6) through the intermediate pressure pipe (7), and the precooling compressor (8) A pre-stage oil separator (9) for separating oil for compressor lubrication from the discharged high-pressure helium gas, and a heat exchanger (1) for cooling the high-pressure helium gas discharged from the pre-stage oil separator (9).
0) and the latter-stage oil separator (1) for further separating lubricating oil from the helium gas discharged from the heat exchanger (10).
1) and an adsorber (12) for adsorbing and removing impurities from the helium gas discharged from the latter-stage oil separator (11) are arranged, and the discharge side of the adsorber (12) is a high-pressure pipe for precooling ( 13) to the precooling high-pressure gas discharge port (14), and the JT high-pressure gas discharge port (14) branched from the pre-cooling high-pressure pipe (13). 1
6), respectively.

The JT high-pressure pipe (15) is branched in parallel to the first and second branch pipes (15a) and (15b) on the way, and the flow rate is adjusted to the first branch pipe (15a). Fixed throttle-type first throttle valve (V1) and a pneumatic first type throttle valve (V1) on the high-pressure gas discharge port (16) side.
An on-off valve (AV1) is provided. On the other hand, the same second throttle valve (V2) and second open / close valve (AV2) are arranged in the second branch pipe (15b), and the second throttle valve (V2) is provided.
The opening degree of is smaller than that of the first throttle valve (V1).

In this embodiment, two JT high-pressure pipes (15) from the precooling compressor (8) to the liquid helium tank (Th) are branched in parallel to form two branch pipes (15a), (15b) and the branch pipes (15a),
Throttle valves (V1) and (V2), which are respectively disposed in (15b) and have different opening degrees, and branch pipes (15a),
Open / close valves (AV1) and (A) for opening and closing (15b) respectively.
V2) and a refrigerant flow rate adjusting mechanism (19) are configured, and each on-off valve (A) of the refrigerant flow rate adjusting mechanism (19) is configured.
By opening and closing V1) and (AV2), the helium gas flow rate from the compressor (8) to the liquid helium tank (Th) is adjusted.

Further, one end of a helium gas supply / discharge pipe (17) is branched and connected to the low pressure pipe (3) between the suction side of the JT compressor (4) and the low pressure gas suction port (2). Is
The other end of the helium gas supply / discharge pipe (17) has a buffer tank (T) for storing the helium gas at a predetermined pressure (PB).
connected to b). Helium gas supply and discharge piping (17)
Is branched in parallel to two branch pipes (17a) and (17b), and one of the branch pipes (17a) has a fixed throttle valve (VA1) for adjusting the flow rate and the throttle valve (VA).
The first low-pressure control valve (LPR1) on the low-pressure pipe (3) side of 1)
While the other branch pipe (17b) is provided with a similar throttle valve (VA2) and a second low pressure control valve (LPR).
2) and are provided. Each low pressure control valve (LPR
1) and (LPR2) automatically open as a pilot pressure when the pressure of the helium gas in the low-pressure pipe (3) (internal pressure of the liquid helium tank (Th)) drops below a set pressure, This low pressure control valve (LPR1), (LP
With the opening of R2), the helium gas in the buffer tank (Tb) is supplied to the low pressure pipe (3) (refrigerant circuit).

In the JT high-pressure pipe (15), a second branch pipe (15b) in which a second throttle valve (V2) is arranged, and a collecting portion of the helium gas supply / discharge pipe (17). Are connected by a helium gas return pipe (18) in which a high pressure control valve (HPR) is arranged. The high pressure control valve (HPR) automatically opens as a pilot pressure when the pressure of the helium gas in the JT high pressure pipe (15) rises above a set pressure. H
By opening the valve (PR), the helium gas in the JT high-pressure pipe (15) (refrigerant circuit) is returned to the buffer tank (Tb).

On the other hand, the refrigerator unit (21)
Includes a pre-cooling refrigerator (22) (expander) connected to the pre-cooling compressor (8) of the compressor unit (1) in a closed circuit.
And a J-T refrigerator (31) connected in series with the J-T compressor (4) and the pre-cooling compressor (8). The pre-cooling refrigerator (22) comprises a GM (Gifford McMahon) cycle refrigerator,
Helium gas is compressed and expanded to precool the helium gas (refrigerant gas) in the JT refrigerator (31). This pre-cooling refrigerator (22) is the above vacuum dewar (D).
And a cylinder (24) having a large and small two-stage structure connected to the case (23). The case (23) has a high pressure gas inlet (26) connected to the high pressure gas discharge port (14) for precooling of the compressor unit (1) through a flexible pipe (25), and an intermediate pressure gas suction port. Low pressure gas outlet (2) connected to (6) via flexible piping (27)
8) and are opened. On the other hand, the cylinder (24) penetrates the side wall of the vacuum dewar (D) and extends to the inside thereof, and the tip of the large diameter portion (24a) thereof is cooled and maintained at a predetermined temperature level in the first heat station (29). ) And the tip of the small diameter portion (24b) is formed in the second heat station (30) which is cooled and held at a temperature level lower than that of the first heat station (29).

That is, although not shown here, in the cylinder (24), each of the heat stations (2
Free type displacers (replacers) that partition and form expansion spaces are reciprocally fitted at positions corresponding to 9) and (30). On the other hand, the above case (2
In 3), a rotary valve that opens and closes each time it rotates,
A valve motor that drives the rotary valve is housed. The rotary valve has the high pressure gas inlet (26).
The helium gas flowing in from is supplied to each expansion space in the cylinder (24), or the helium gas expanded in each expansion space is switched to be discharged from the low pressure gas outlet (28). Then, by opening and closing this rotary valve, the high-pressure helium gas is expanded by Simon in each expansion space in the cylinder (24), and a temperature drop due to the expansion causes a cryogenic level of cold to be generated, and the cold is cooled by the cylinder (24). First and second heat stations (29), (3
Hold at 0). That is, in the pre-cooling refrigerator (22),
The high-pressure helium gas discharged from the pre-cooling compressor (8) is adiabatically expanded to heat stations (29), (3).
0) to lower the temperature to precool later-described precoolers (36) and (37) in the J-T refrigerator (31),
The expanded low pressure helium gas is returned to the compressor (8) and recompressed.

On the other hand, the JT refrigerator (31) has about 4
A refrigerator that expands helium gas by Joule-Thomson to generate K-level coldness, the refrigerator (31) being a first refrigerator arranged in the vacuum dewar (D).
-The 3rd JT heat exchanger (32)-(34) is provided. Each of the J-T heat exchangers (32) to (34) exchanges heat between the helium gases passing through the primary side and the secondary side, respectively.
The secondary side is connected to the JT high-pressure gas discharge port (16) of the compressor unit (1) via a flexible pipe (35). In addition, the first and second JT heat exchangers (3
The primary side of each of 2) and (33) is connected to the pre-cooling refrigerator (2
It is connected via a first precooler (36) arranged on the outer periphery of the first heat station (29) of the cylinder (24) in (2). Similarly, the respective primary sides of the second and third J-T heat exchangers (33), (34) are connected via the second precooler (37) arranged on the outer periphery of the second heat station (30). Has been done. Further, the primary side of the third J-T heat exchanger (34) is connected to a J-T valve (38) for expanding the high-pressure helium gas into the adsorber (3).
9). The opening of the JT valve (38) is adjusted from the outside of the vacuum dewar (D) by the operation rod (38a). The JT valve (38) is a liquid helium return pipe (40) made of a stainless steel pipe.
Through the helium tank (Th).
The inside of the helium tank (Th) is connected to the secondary side of the third JT heat exchanger (34) through a helium gas suction pipe (41) made of the same stainless steel pipe. And, 2 of this 3rd J-T heat exchanger (34)
The secondary side goes through the secondary side of the second JT heat exchanger (33) to the first side.
It is connected to the secondary side of the JT heat exchanger (32) and
The secondary side of the JT heat exchanger (32) is connected to the low pressure gas inlet (2) of the compressor unit (1) via a flexible pipe (42).

That is, the JT refrigerator (31) includes flexible pipes (35) and (42), low pressure pipe (3), both compressors (4) and (8), and JT high pressure pipe (15). To the helium tank (Th) through a liquid helium return pipe (40) and a helium gas suction pipe (41). Helium gas evaporated in (Th) is sucked into the refrigerant circuit from the gas suction pipe (41) and passed through each of the secondary sides of the third to first J-T heat exchangers (34) to (32) for JT and The pre-cooling compressors (4) and (8) are sucked and compressed. Further, the high pressure helium gas compressed by the precooling compressor (8) is supplied to the compressor (4) side at low temperature and low pressure in the first to third JT heat exchangers (32) to (34). Heat exchange with helium gas and first
And the second precoolers (36) and (37) respectively for the first and second heat stations (29) of the cylinder (24),
After cooling at (30), the JT valve (38)
Expanded Thomson into helium in a liquid state of about 4K,
The liquid helium is returned to the tank (Th) via the liquid helium return pipe (40).

The first and second on-off valves (AV1), (A
V2) is connected to a manifold unit (52) that receives a control signal from a power supply control unit (51) that controls the operating frequencies of the compressors (4) and (8) and switches the action or suspension of air pressure. . The power supply control unit (51) includes a high pressure sensor (HP) for detecting the pressure of the high pressure helium gas discharged from the precooling compressor (8).
S), the detection signal of the low pressure sensor (LPS) for detecting the pressure of the low pressure helium gas in the low pressure pipe (3) communicating with the suction side of the JT compressor (4), and the helium gas supply. Pressure in the drain pipe (17) (buffer tank (Tb)
The detection signal of the buffer tank pressure sensor (MPS) that detects the internal pressure (PB) of the compressor and the operation signals of the three protection switches (SS1) to (SS3) in the compressor unit (1) are input.

The control operation performed by the power supply control unit (51) will be described with reference to FIGS. 2 and 3. First, in step ST1, it is determined whether to switch manually or automatically,
When this judgment is manual, after the operation button is turned ON in step ST2, when it is automatic, in step ST2
After inputting the external operation signal in step 3,
Proceed to T4. In step ST4, it is determined whether the operation mode is switched. If the determination is in the low speed mode, the operation frequency f of the compressors (4) and (8) is set to, for example, f = 40 Hz in step ST5, and the first opening / closing valve ( After opening AV1) and closing the second on-off valve (AV2), the protection switch (SS) of the compressor unit (1) is opened at step ST6.
It is determined whether 1) to (SS3) are activated. When this determination is YES, after displaying an abnormal state in step ST22, the process proceeds to step ST23, and the compressors (4) and (8) are stopped. Then, step ST2
In step 4, the first on-off valve (AV1) is closed to stop the operation.

When the determination in step ST6 is NO, the low speed operation is executed in step ST7, the stop button is turned on in step ST21, and then the process proceeds to step ST23.

When the determination in step ST4 is in the normal mode, the operating frequency f of the compressors (4) and (8) is set to, for example, f = 55 Hz in step ST8, and the first opening / closing valve (AV1) is opened. After closing the second on-off valve (AV2), the process proceeds to step ST9, and similarly to step ST6, the protection switch (SS1) of the compressor unit (1).
~ (SS3) determines whether or not activated. If the determination is YES, the process proceeds to step ST22, but if the determination is NO, the buffer tank pressure (PB
) Is lower than 3.0 kg / cm ^2, for example, and if the determination is NO at PB ≧ 3.0, the normal operation is executed in step ST20, and then the process proceeds to step ST21. YES in step ST10
In case of, the low speed operation is executed in step ST11,
At step ST12, it is determined whether or not the buffer tank pressure (PB) is higher than 4.0 kg / cm ^2, for example, and if the determination is NO at PB ≤4.0, the above step S12 is performed.
Return to T11, but if YES, go to step ST2
Go to 0.

Further, when the determination in step ST4 is in the excitation / demagnetization mode, the operating frequency f of the compressors (4) and (8) is set to, for example, f = 70 Hz in step ST13, and the first and second opening / closing valves ( After closing both AV1) and (AV2), the process proceeds to step ST14, and it is determined whether or not the protection switches (SS1) to (SS3) of the compressor unit (1) have been actuated, as in step ST6. If the determination is YES, the process proceeds to step ST22, but if the determination is NO, the process proceeds to step ST15 to execute the demagnetization of the superconducting magnet. Then, step ST16
It is determined whether or not the excitation / demagnetization has ended. If this determination is NO, the process returns to step ST15, but if the determination is YES, then in step ST17 the first set time (T1)
It is determined whether (for example, T1 = 60 seconds) has elapsed. When this judgment is NO, the same step ST17 is repeated, but when the judgment is YES, the routine proceeds to step ST18, where the first on-off valve (AV1) is closed as it is, and the second
After opening only the on-off valve (AV2), step ST1
9 and proceed to the second set time (T2) (for example, T2 = 20
Second) has elapsed. When this determination is NO, steps ST18 and ST19 are repeated, but when the determination is YES, the process proceeds to step ST20.

[0040] In this embodiment, the above step ST4, demagnetization operation detecting means for detecting that perform demagnetization of the superconducting magnet in the linear motor car or the like (53) is configured.

Further, steps ST13, ST15 to ST
20 receives the output signal of the excitation / demagnetization operation detection means (53), and during the excitation / demagnetization of the superconducting magnet, both the first and second on-off valves (AV1), (AV2) are closed to close the precooling compressor ( When the helium gas flow rate from 8) to the liquid helium tank (Th) is switched from the normal flow rate to 0 and the first set time (T1) elapses after the superconducting magnet has been demagnetized, the second set time (T2) elapses. Until then, only the second opening / closing valve (AV2) is opened to switch the helium gas flow rate to a set flow rate that is lower than the normal flow rate, and then only the first opening / closing valve (AV1) is opened to set the helium gas flow rate to the normal flow rate. A control means (54) is configured to control the refrigerant flow rate adjusting mechanism (19) so as to return it.

Next, the operation of the above embodiment will be described. In the steady state in which the superconducting magnet of the linear motor car is operated, the superconducting coil of the superconducting magnet is cooled and maintained below the critical temperature by the liquid helium in the helium tank (Th). Further, the helium gas evaporated in the helium tank (Th) is sucked from the helium gas suction pipe (41) opening in the tank (Th) and supplied to the refrigerant circuit of the refrigerator (R), where it is compressed and compressed. It is cooled by expansion and liquefied. The liquid helium is returned to the tank (Th) through the liquid helium return pipe (40). As a result, a predetermined amount or more of liquid helium is stored in the tank (Th), and the superconducting coil is stably cooled below the critical temperature.

The operation of the refrigerator (R) will be described in more detail. In the steady operation state, a part of the high-pressure helium gas supplied from the precooling compressor (8) of the compressor unit (1) is precooled. The first heat station (29) expands in each expansion space in the cylinder (24) of the refrigerator (22) (expander), and the first heat station (29) reaches a predetermined temperature level due to the temperature drop accompanying the expansion of the gas, and the second heat station. (30) are each cooled to a lower temperature level than the first heat station (29). The helium gas expanded in the expansion space returns to the compressor unit (1) and is sucked into the precooling compressor (8) via the intermediate pressure pipe (7) and compressed.

On the other hand, J- in the compressor unit (1)
The first on-off valve (AV1) of the T high-pressure pipe (15) is opened while the second on-off valve (AV2) is closed, so that the high-pressure helium gas discharged from the precooling compressor (8) is discharged. The remainder enters the primary side of the first JT heat exchanger (32) of the JT refrigerator (31) via the first throttle valve (V1) of the JT high pressure pipe (15), Then, heat is exchanged with the low pressure helium gas on the secondary side toward the compressor (4) side, and the temperature is kept at room temperature 300.
It is cooled from K to about 50K, and thereafter, it is further cooled by entering the first heat station (29) of the precooling refrigerator (22) and the first precooler (36) on the outer periphery. This cooled gas enters the primary side of the second J-T heat exchanger (33) and is cooled to about 15 K by heat exchange with the low pressure helium gas on the secondary side as well, and then the precooling refrigerator ( 22) second heat station (30) outer peripheral second precooler (3
It goes into 7) and is cooled further. After this, the gas is the 3rd J
It enters the primary side of the -T heat exchanger (34) and is further cooled by heat exchange with the low pressure helium gas on the secondary side before reaching the JT valve (38). In this JT valve (38), the high-pressure helium gas is throttled and expanded by Joule-Thomson into liquid helium of about 4K, and this liquid helium passes through the liquid helium return pipe (40) to the tank (Th). Is supplied to. Further, the helium gas evaporated in the tank (Th) is sucked into the secondary side of the third J-T heat exchanger (34) through the helium gas suction pipe (41), and the second and first J-T heats are absorbed. It is sucked into the JT compressor (4) via the secondary sides of the exchangers (33) and (32) and compressed.

When demagnetization for stopping the generation of the magnetic field by the superconducting magnet or excitation by applying a current is performed for maintenance or inspection of the linear motor car, as shown in FIG. The machine (R) is in the excitation / demagnetization mode, and each compressor (4) in the refrigerator (R),
The operating frequency f of (8) rises from f = 55 Hz to 70 Hz, and as a result, the suction amount of the evaporated helium gas in the liquid helium tank (Th) to the JT compressors (4) and (8), that is, The outflow amount of the evaporated helium gas from the tank (Th) increases. Also, the J-T of the compressor unit (1)
The second on-off valve (AV2) in the high-pressure pipe (15) is closed as it is, but the first (AV1) is switched from the open state to the closed state.
By closing the valve V2), the JT high-pressure pipe (15) is closed, and the amount of helium flowing into the liquid helium tank (Th) becomes zero. That is, while the outflow amount of the evaporated helium gas from the liquid helium tank (Th) increases, the inflow amount is 0
Therefore, the internal pressure decreases, and in this state, the demagnetization of the superconducting magnet of the linear motor car is executed. Therefore, even if the heat load increases due to the execution of the demagnetization of the superconducting magnet, the rise of the internal pressure of the liquid helium tank (Th) is suppressed, so that the safety valve can be prevented from operating.

When the excitation / demagnetization of the superconducting magnet is completed and the first set time (T1) elapses thereafter, the first on-off valve (A
V1) is maintained in the closed state as it is, but the second opening / closing valve (AV2) is opened, whereby the high-pressure helium gas flows through the second throttle valve (V2) of the JT high-pressure pipe (15). Enter via liquid helium tank (Th). Since the opening degree of the second throttle valve (V2) is smaller than that of the first throttle valve (V1), the flow rate of helium gas supplied to the liquid helium tank (Th) is maintained at a set flow rate lower than the normal flow rate.
After that, when the second set time (T2) elapses, only the first opening / closing valve (AV1) is opened and the helium gas flow rate is returned to the normal flow rate as before.

That is, in this embodiment, when the helium gas flow rate is returned to the normal flow rate determined by the opening degree of the first throttle valve (V1) after the demagnetization of the superconducting magnet of the linear motor car is completed, first, the helium gas flow rate is set. Is switched to a set flow rate (flow rate determined by the opening degree of the second throttle valve (V2)) that is smaller than the normal flow rate, and then returned to the normal flow rate. Therefore, while this flow rate is at the set flow rate, the liquid is discharged from the compressor (8). The flow rate of the helium gas reaching the helium tank (Th) can be reduced by lowering the pressure thereof. As a result, as shown in FIG. 6, it is possible to effectively prevent the internal pressure of the liquid helium tank (Th) from rising beyond the peak value during demagnetization as in the conventional case, and the demagnetization mode of the refrigerator (R). Driving time can be shortened. As a result, the compressor (4),
The time for raising the operating frequency of (8) is short, and the durability can be improved. In addition, refrigerator (R)
Since the operating time of the excitation / demagnetization mode is short, the flow rate balance between the helium gas directed to the liquid helium gas (Th) and the helium gas returned from the tank (Th) to the compressor (4) in the JT side refrigerant circuit There is no fear that the temperature of the suction gas to the compressor will drop due to the collapse of the frost and the frost will adhere to the flexible pipe (42). Also, liquid helium tank (T
The evaporation amount of helium gas in h) can be reduced, and further, the recovery amount of helium gas in the buffer tank (Tb) can be reduced.

(Embodiment 2) FIGS. 7 to 10 show Embodiment 2 (note that the same parts as those in FIGS. 2 to 5 are designated by the same reference numerals and detailed description thereof will be omitted), In No. 1, the flow rate of the helium gas is set to 0 for the demagnetization of the superconducting magnet, whereas a predetermined flow rate is made to flow.

That is, in this embodiment, as shown in FIG. 9, the JT high-pressure pipe (15) in the compressor unit (1) is provided with three branch pipes (15) (1 to 3) on the way.
a) to (15b) are branched in parallel, and the first branch pipe (1
5a) is a fixed first throttle valve (V
1) and a pneumatic first on-off valve (AV1) are provided. A similar second throttle valve (V
2) and the second on-off valve (AV2), and the third branch pipe (15c) is also provided with the same third throttle valve (V3) and third on-off valve (AV3). Comparing the opening degrees of these three throttle valves (V1) to (V3), the opening degree of the second throttle valve (V2) is the smallest, and then the third throttle valve (V3) and the first throttle valve (V1). The opening is set to be large in order.

The control operation of the power supply control unit (51) is basically the same as that of the first embodiment (see FIGS. 2 and 3), except for the following parts. That is, as shown in FIGS. 7 and 8, first, when the determination in step ST4 is the excitation / demagnetization mode, in step ST13, the compressor (4),
The operating frequency f of (8) is set to, for example, f = 70 Hz,
After closing both the first and third opening / closing valves (AV1) and (AV3) and opening only the second opening / closing valve (AV2),
It proceeds to step ST14.

In step ST18, the first on-off valve (AV1) is closed, the second on-off valve (AV2) is switched from the open state to the closed state, and the third on-off valve (A) is opened.
After opening V3), the process proceeds to step ST19.

Further, during the steady operation of step ST20, only the first opening / closing valve (AV1) is opened.

Therefore, in this embodiment, the control means (54) is constituted by the steps ST13, ST15 to ST20 of the flow shown in FIG. 7 and FIG.
4) receives the output signal of the excitation / demagnetization operation detection means (53), and during the excitation / demagnetization of the superconducting magnet, the first and third on-off valves (A).
Both V1) and (AV3) are closed and the second on-off valve (AV
2) only open the helium gas flow rate from the precooling compressor (8) to the liquid helium tank (Th) from the normal flow rate set by the first throttle valve (V1) to the second throttle valve (V).
After switching to the first set flow rate set in 2) and ending the demagnetization of the superconducting magnet, the first set time (T1) passes,
Until the second set time (T2) elapses, only the third opening / closing valve (AV3) is opened so that the helium gas flow rate is lower than the normal flow rate and higher than the first set flow rate (third throttle). The flow rate is set to the value set by the valve (V3), and then only the first opening / closing valve (AV1) is opened to control the refrigerant flow rate adjusting mechanism (19) so as to return the helium gas flow rate to the normal flow rate.

Therefore, in the case of this embodiment, as shown in FIG. 10, in the operating state of the superconducting magnet in the linear motor car, only the first opening / closing valve (AV1) of the JT high-pressure pipe (15) is opened. The helium gas flow rate is set to the normal flow rate. And when the superconducting magnet is demagnetized,
During the execution, only the second opening / closing valve (AV2) of the JT high-pressure pipe (15) is opened to set the flow rate of helium gas to the first set flow rate. This excitation / demagnetization ends, and then the first
When the set time (T1) has elapsed, the second opening / closing valve (AV2)
Is closed and the third on-off valve (AV3) is opened instead, so that high-pressure helium gas is passed through the third throttle valve (V3) of the JT high-pressure pipe (15) to the liquid helium tank. (Th) is entered, and the flow rate of the helium gas at that time is the second set flow rate set by the third throttle valve (V3). Further, when the second set time (T2) elapses thereafter, only the first opening / closing valve (AV1) is opened and the helium gas flow rate is returned to the original normal flow rate. Therefore, also in this embodiment, the same operational effect as that of the above-described first embodiment can be obtained.

In each of the above embodiments, the JT high-pressure pipe (15) is provided with a plurality of branch pipes (15a), (15b), ...
To the branch pipes (15a), (15b), ...
The flow rate of the helium gas is adjusted by switching the open / close valves (AV1), (AV2), ...
It is also possible to perform the same flow rate adjustment by combining (AV2), ... And controlling the opening and closing. Also, J-T
It is also possible to use one pneumatic high-pressure pipe (15) and use a pneumatic proportional control valve whose opening is variable, and the same effect can be obtained.

[0056]

As described above, in the invention of claim 1 or 4, the refrigerant circuit is opened in the tank for storing the liquefied refrigerant for cooling and holding the superconducting magnet below the critical temperature, and the refrigerant gas evaporated in the tank is opened. Refrigerant flow rate adjustment that adjusts the refrigerant flow rate from the compressor to the refrigerant tank for the cryogenic refrigerator in which the liquefied refrigerant is returned to the tank by taking it into the refrigerant circuit and cooling and reliquefying it by compression and expansion. When a means is provided to demagnetize the superconducting magnet, the refrigerant flow rate from the compressor to the refrigerant tank is set to 0 during execution, and when the refrigerant flow rate is returned to the normal flow rate after the end of the demagnetization, once, After switching to a set flow rate that is lower than the normal flow rate, the normal flow rate is restored. Further, in the invention of claim 2 or 5, during the excitation / demagnetization of the superconducting magnet, the refrigerant flow rate from the compressor to the refrigerant tank is set to a first set flow rate which is smaller than the normal flow rate, and the refrigerant flow rate is normally set after the end of the demagnetization. When returning to the flow rate, the flow rate is once returned to the normal flow rate after switching to the second set flow rate which is lower than the normal flow rate and higher than the first set flow rate. Therefore, according to these inventions, the superconducting magnetism
When the flow rate of the refrigerant is returned to the normal flow rate after the stone is demagnetized, the pressure of the refrigerant from the compressor to the refrigerant tank is reduced to reduce the flow rate while this flow rate is at the intermediate set flow rate, and the internal pressure of the refrigerant tank is excited. It is possible to effectively suppress the rise above the peak value during demagnetization, shorten the operating time of the demagnetization operation mode of the refrigerator, improve the durability of the compressor and prevent frosting of the connecting pipe. In addition, it is possible to reduce the amount of refrigerant evaporated in the tank and the amount of refrigerant collected in the buffer tank.

According to the third aspect of the present invention, a plurality of branch pipes are formed by branching the refrigerant pipes from the compressor to the refrigerant tank in parallel, and throttle valves that are arranged in the respective branch pipes and have different opening degrees. An opening / closing valve for opening / closing each branch pipe is provided, and each opening / closing valve is opened / closed to adjust the refrigerant flow rate from the compressor to the refrigerant tank, thereby facilitating a desirable configuration of the refrigerant flow rate adjusting means. Can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a flowchart showing the first half of the control operation performed by the power supply control unit according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the latter half of the control operation performed by the power supply control unit.

FIG. 4 is a refrigerant circuit diagram showing the overall configuration of a refrigerator for a linear motor car in the first embodiment.

FIG. 5 is a time chart showing switching between opening and closing of the on-off valve and changes in the helium gas flow rate associated therewith in the first embodiment.

FIG. 6 is a characteristic diagram showing changes in the internal pressure of the liquid helium tank when the superconducting magnet is excited and demagnetized in Example 1.

FIG. 7 is a view corresponding to FIG. 2 showing a second embodiment.

FIG. 8 is a view corresponding to FIG. 3 showing a second embodiment.

9 is a view corresponding to FIG. 4 showing the second embodiment.

10 is a view corresponding to FIG. 5 showing the second embodiment.

[Explanation of reference signs] (R) Refrigerator (1) Compressor unit (4), (8) Compressor (15) JT high-pressure pipe (refrigerant pipe) (15a), (15b), (15c) Branch Piping (AV1), (AV2), (AV3) Open / close valves (V1), (V2), (V3) Throttle valve (19) Refrigerant flow rate adjusting mechanism (refrigerant flow rate adjusting means) (21) Refrigerator unit (22) Precooling Refrigerator (31) JT refrigerator (38) JT valve (expansion means) (51) Power supply control unit (53) Excitation / demagnetization operation detection means (54) Control means (Th) Liquid helium tank (refrigerant tank) (Tb) Buffer tank

Claims (5)

[Claims] 1. A refrigerant tank (T that stores a liquid refrigerant for cooling and maintaining a superconducting magnet of a linear motor car at a critical temperature or lower).
In h), compressors (4), (8) and expansion means (38)
Of the refrigerant tank (T
The gas refrigerant evaporated in h) is sucked into the refrigerant circuit, compressed by the compressors (4) and (8), and then expanded by the expansion means (38), and a liquid refrigerant is generated by the temperature drop due to the expansion, thereby generating the refrigerant. In a refrigerator for a linear motor car that is returned to the inside of a tank (Th), refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), The refrigerant flow rate reaching the refrigerant tank (Th) during the excitation / demagnetization of the superconducting magnet by receiving the output signal of the excitation / demagnetization operation detection means (53) for detecting the excitation / demagnetization of the superconducting magnet and the detection means (53). Is switched from the normal flow rate to 0, and after the excitation / demagnetization is finished, the control means (54) for controlling the refrigerant flow rate adjusting means (19) so as to return the coolant flow rate to the normal flow rate after switching to the set flow rate smaller than the normal flow rate. ) And Operation control system for a linear motor car refrigerator, characterized in that the. 2. A refrigerant tank (T that stores a liquid refrigerant that cools and holds a superconducting magnet of a linear motor car below a critical temperature).
In h), compressors (4), (8) and expansion means (38)
Of the refrigerant tank (T
h) The gas refrigerant evaporated in the h) is drawn into the refrigerant circuit, compressed by the compressors (4) and (8) and then expanded by the expansion means (38), and the liquid refrigerant is generated by the temperature drop due to the expansion, thereby generating the refrigerant. In a refrigerator for a linear motor car that is returned to the inside of a tank (Th), a refrigerant flow rate adjusting means (19) for adjusting the refrigerant flow rate from the compressors (4) and (8) to the refrigerant tank (Th), The refrigerant flow rate reaching the refrigerant tank (Th) during the excitation / demagnetization of the superconducting magnet by receiving the output signal of the excitation / demagnetization operation detection means (53) for detecting the excitation / demagnetization of the superconducting magnet and the detection means (53). Is switched from the normal flow rate to a first set flow rate lower than the normal flow rate, and after the excitation / demagnetization is completed, the refrigerant flow rate is switched to the second set flow rate lower than the normal flow rate and higher than the first set flow rate, Return to flow rate Uni the refrigerant flow rate adjusting means (19) control means for controlling (54) and the operation control system for a linear motor car refrigerator, characterized in that a. 3. The operation control device for a refrigerator for a linear motor car according to claim 1 or 2, wherein the refrigerant flow rate adjusting means (19) is a refrigerant from the compressors (4), (8) to the refrigerant tank (Th). A plurality of branch pipes (15a), (15b) formed by branching the pipe (15) in parallel,
, And throttle valves (V1), which are respectively arranged in the branch pipes (15a), (15b), ...
(V2), ... and each branch pipe (15a), (15b),
Open / close valves (AV1), (AV2), which open and close respectively ...
... and each open / close valve (AV1), (AV2),
The compressors (4), (8) are switched by opening and closing.
An operation control device for a refrigerator for a linear motor car, which is configured to adjust a refrigerant flow rate from a refrigerant tank to a refrigerant tank (Th). 4. A refrigerant tank (T that stores a liquid refrigerant that cools and holds a superconducting magnet of a linear motor car below a critical temperature).
In h), compressors (4), (8) and expansion means (38)
Of the refrigerant tank (T
h) The gas refrigerant evaporated in the h) is drawn into the refrigerant circuit, compressed by the compressors (4) and (8) and then expanded by the expansion means (38), and the liquid refrigerant is generated by the temperature drop due to the expansion, thereby generating the refrigerant. A method for controlling the operation of a refrigerator for a linear motor car that is returned to the inside of a tank (Th), wherein when the superconducting magnet is demagnetized, the compressors (4) and (8) reach the refrigerant tank (Th). A method for controlling operation of a refrigerator for a linear motor car, comprising: switching a refrigerant flow rate from a normal flow rate to 0 and, when excitation / demagnetization is completed, switching the refrigerant flow rate to a set flow rate smaller than the normal flow rate and then returning to the normal flow rate. 5. A refrigerant tank (T for storing a liquid refrigerant for cooling and maintaining a superconducting magnet of a linear motor car at a critical temperature or lower).
In h), compressors (4), (8) and expansion means (38)
Of the refrigerant tank (T
h) The gas refrigerant evaporated in the h) is drawn into the refrigerant circuit, compressed by the compressors (4) and (8) and then expanded by the expansion means (38), and the liquid refrigerant is generated by the temperature drop due to the expansion, thereby generating the refrigerant. A method for controlling the operation of a refrigerator for a linear motor car that is returned to the inside of a tank (Th), wherein when the superconducting magnet is demagnetized, the compressors (4) and (8) reach the refrigerant tank (Th). When the refrigerant flow rate is switched from the normal flow rate to the first set flow rate which is smaller than the normal flow rate, and when the excitation / demagnetization is completed, the refrigerant flow rate is switched to the second set flow rate which is smaller than the normal flow rate and larger than the first set flow rate. A method for controlling the operation of a refrigerator for a linear motor car, which is characterized by returning to a normal flow rate.